1. Field of the Invention
The present invention relates to an apparatus for synthesizing diamond from a gas phase. More particularly, it relates to an apparatus wherein the diamond precipitating area is enlarged.
2. Discussion of Background
The following apparatus have been known for the synthesis of diamond by a microwave plasma method.
FIGS. 6 to 8 illustrate apparatus for synthesizing diamond by means of a microwave plasma. FIGS. 6 and 7 illustrate apparatus for synthesizing diamond wherein a microwave generated by a microwave oscillator 3 is conducted to a reaction chamber 5 by a wave guide 4 to generate a plasma in a gas mixture of hydrogen and a hydrocarbon gas, and a substrate 7 provided in the reaction chamber 5 is heated by a heating furnace 9 or an infrared lamp image furnace 10 to decompose the hydrocarbon to form diamond on the substrate 7. In FIG. 8, a microwave is generated by a microwave oscillator 3 and introduced to a reaction chamber 5 via a wave guide 4 to generate a plasma in a gas mixture of hydrogen and a hydrocarbon gas supplied from a gas supply device 1, around a substrate 7 provided at the intersection of the reaction chamber 5 and the wave guide 4 and at the same time the substrate 7 is heated. Diamond precipitates on the substrate 7 by the thermal decomposition of the hydrocarbon on the heated substrate 7. Reference numerals 12, 13, 14, 15 and 16 indicate cocks.
According to such conventional methods, however, the microwave is introduced from only one direction, and the plasma forming area is restricted by the wavelength of the microwave, whereby it is difficult to enlarge the size of the reaction chamber 5 beyond one half of the wavelength of the microwave. Accordingly, the diamond precipitating area is likewise restricted to a diameter corresponding to one half of the microwave at the maximum.